With JS

A declarative way to add or remove attributes and classes on HTML elements when JavaScript is loaded. Extensible to allow running other kind of updates.

Why

Some attributes, classes and styles are only relevant once JavaScript has loaded:

ARIA properties or roles setting expectations for assistive technologies that are only fullfiled by JavaScript
Some fallback HTML that needs hiding once JavaScript is there, because an enhanced widget takes over the feature
Or inversely some HTML that needs revealing to provide a better experience, but only when JavaScript is present.

Because there's no guarantee JavaScript will load, they should not be present in the HTML that's downloaded by browsers. This library provides a declarative way (through either data attributes or classes) to quickly amend the initial markup once JavaScript has loaded, ensuring a clean experience when it doesn't.

Usage

The library will look for elements marked by specific classes in your HTML. Out of the box, withJS allows you to run the following operations by adding classes to your HTML elements:

Removing the element from the DOM: js-with-js--remove
Adding an attribute: js-with-js--add-attribute__role--tab will add the role="tab" to the element. More generally, you can use js-with-js--add-attribute__<attribute-name>--<attribute-value>.
Removing an attribute: js-with-js--remove-attribute__hidden will remove the hidden attribute from the element. More generally, you can use js-with-js--remove-attribute__<attribute-name>
Adding a class: js-with-js--add-class__sr-only will add the sr-only class to the element. More generally, you can use js-with-js--add-class__<class-name>
Removing a class js-with-js--remove-class__margin-top-0 will remove the margin-top-0 class. More generally, you can use js-with-js--remove-class__<class-name>

You might have noticed the js-with-js--<operation-name>__<argument1>--<argument2> in all these classes. You can extend the library to provide your own operations to suit your needs (see bellow).

Installation

Install the package with your favourite package manager

npm install @cookieshq/with-js

yarn add @cookieshq/with-js

Import the library and call withJS() in your project:
- using ES6 imports
```
import { withJS } from '@cookieshq/with-js/src/index'
withJS();
```
  Note: The package.json file does have a module field pointing to src/index.js which should allow to just import @cookieshq/with-js. However, specifying the whole path in the import was the most reliable way to get it working across the major bundlers (Webpack, Rollup and Parcel).
- using Common JS imports
```
const withJS = require('@cookieshq/with-js')
withJS();
```
- with a <script> tag in your HTML
```
<script src="https://unpkg.com/@cookieshq/with-js/dist/with-js.iife.min.js" defer></script>
<script async>
  document.addEventListener('DOMContentLoaded', function() {
    withJS();
  });
</script>
```

You have to explicitly call withJS() for the updates to get applied. This lets you be in control of when and with which options it runs.

JS API

Without any arguments, withJS() will hunt for all elements with a class that contains js-with-js-- in the document. You can also:

pick a specific element to update with withJS(element)
select other elements in the DOM with a CSS selector withJS(selector)
restrict where withJS looks for the elements to update with withJS({parent: element})
which can also be combined with using your own selector withJS(selector, {parent:element}), or less verbosely withJS(selector, parentElement)

Extending the library

Internally the library run()s the updates() it extracts from each target element(s). You can override both behaviors by providing your own functions in a final hash parameter:

withJs({run: customRunFunction, updates: customUpdatesFunction});
withJs({parent: element, run: customRunFunction, updates: customUpdatesFunction});
withJs(element,{run: customRunFunction, updates: customUpdatesFunction});
withJs(selector,{run: customRunFunction, updates: customUpdatesFunction});
withJs(selector, parent,{run: customRunFunction, updates: customUpdatesFunction});

Adding extra operations

You can add extra options by providing your own run function that passes custom list of operation to the default implementation.

import { withJS, applyUpdates,AVAILABLE_OPERATIONS } from '@cookieshq/with-js';

withJS({
  run: function(operations, el) {
    return applyUpdates(operations, el, {
      availableOperations: {
        ...AVAILABLE_OPERATIONS,
        // This would now allow things like `js-with-js--set-style__display--none`
        'set-style': function(element,property, value) {
          element.style[property] = value;
        }
      }
    })
  }
})

Customizing the class pattern

Maybe you find the js-with-js-- prefix a bit verbose, or prefer different separators. You can provide a custom updates function that provides different options to the default implementation.

import { withJS, getUpdatesFromClasses } from '@cookieshq/with-js';

withJS({
  updates: function(el) {
    // This would let you have class names like: `js--add-attribute:role,tabpanel`
    // As we're not looking to use the class for styling, the "special" characters
    // in the class won't be much of a bother.
    return getUpdatesFromClasses({
      marker: 'js--',
      operationToArgumentsSeparator: ':',
      argumentToArgumentSeparator: ','
    })
  },
  target: '[class*="js--"]'
})

Tooling

The project is build with Rollup, with Babel for compiling to ES5.
Tests are run with Ava
Linting with ESLint is set up on the project and should be triggered on commit thanks to Husky and lint-staged
The project uses np to manage NPM releases

NPM Scripts

The build commands are managed through npm scripts, mostly pass through to one of the modules above:

clean to clean the dist directory
lint for linting the JS files
test for running the tests
build for building the browser and CommonJS files. It'll trigger the postbuild script to minify the browser build
release triggers a release to NPM. It'll automatically run prepack when creating the package to build the latest version of the library